Restoration Primer: Fallen Arches

Fallen Arches
by Wm. Ward Bucher
Masonry walls are most likely to fail
around the top of window and door
openings. This may be because of
beam failure, but it probably is a case
of arch failure.
Arches as first used by the Romans
rarely failed, because they were
semicircular. But as square windows
and doors became fashionable, there
were more and more arch problems.
The flatter an arch is, the more likely
the top of the arch fall downward.
Typically, they will jam in the
opening after moving 1/4 inch or so.
If the abutments continue to
spread, however, the bricks may fall
out.
Jack arches are particularly
susceptible to this kind of failure. In
a jack arch, the bottom